With Lehman Brothers recently listing their first ETNs with a focus on the commodities and private equity sectors, both the Wall Street Journal and Investors' Business Daily interviewed Warun Kumar, their managing director of structured investments for the Americas.

He said that they chose to use ETNs rather than ETFs because the investment bank has more expertise in debt offerings, and that commodities and private equity are harder to track with traditional ETFs because most indexes are based on equities, so an investor has to buy stocks linked to that commodity to get exposure.

Kumar also stated that they chose the commodities and private equity sectors because they aren't covered by many ETFs or ETNs, though there are a number of commodity ETNs already.

Finally, Kumar expressed his opinion on the growing competition between ETFs and ETNs. He said, "ETNs are the better wrappers for investing in commodities and alternative-asset classes. As ETFs get into more illiquid and complex asset classes, ETNs look like the better format."